function get(url,callback) {
    var ajax = new XMLHttpRequest();
    ajax.onreadystatechange = ()=>{
        if (ajax.readyState == 4 &&  ajax.status == 200){
            var json= ajax.responseText;
            var result = JSON.parse(json);
            callback(result);
        }
    }
    ajax.open("get",url);
    ajax.send();
}

function post(url,data,callback) {
    var ajax = new XMLHttpRequest();
    ajax.onreadystatechange = ()=>{
        if (ajax.readyState == 4 &&  ajax.status == 200){
            var json= ajax.responseText;
            var result = JSON.parse(json);
            callback(result);
        }
    }
    ajax.open("post",url);
    // //设置提交数据内容类型
    // if(data instanceof String){
    //     //表单提交参数
    //     ajax.setRequestHeader("Content-Type","application/x-www-form-urlencoded")
    // }else if(data instanceof FormData){
    //     //文件上传
    //     ajax.setRequestHeader("Content-Type","multipart/form-data")
    // }
    ajax.send(data);
}